It is known to make pressurized-water, boiling-water, and pressurized-gas nuclear reactors with a shield surrounding the pressurized core, in order to protect the surroundings should the core burst. Such a burst shield is disclosed in the above cited copending application and in U.S. Pat. No. 3,734,827 issued May 22, 1973 to Franz SCHILLING.
As a rule it has been found necessary to provide an inspection cavity between the pressurized core and the burst shield. A test head, such as an ultrasonic transducer, is introduced in this cavity to detect developing flaws or cracks in core. In the above-cited copending application there is described a burst shield formed of a plurality of cast-iron segments, the side walls of the shield being formed by elements having the shape of segments of a cylindrical annulus or sleeve, and the end walls being formed of cast-iron segments of a circle. Circumferential and longitudinal prestressing elements secure the hollow cast-iron elements together to form an extremely strong burst shield. This type of shield is substantially lighter and cheaper to manufacture than the hitherto known shield which has to be made in situ. A plurality of spacer elements constitute a lining which completely fills the inspection cavity, so that the cover or face of the shield must be removed in order to withdraw these spacer elements so that the core can be inspected. This is made substantially more difficult by the fact that these elements are all prestressed together, and any release of the prestressing force would cause the various parts to move relative to one another, thereby creating a considerable leak potential.